1. Field of the Invention
This invention relates to data networks and, more particularly, to topology parameter broadcasts and advertisements provided in the data networks.
2. Description of the Related Art
Data communication networks involve a collection of nodes and links. The nodes, also known as network elements, provide routing and switching functions, whereas the links provide the transmission facility between neighboring nodes. Nodes typically store information about the network in order to be able to route data efficiently and effectively through the network. The stored information is topological and includes sufficient data to define each link state.
In order to keep the network operating properly as it dynamically changes, it is necessary to update the stored network topology information on some periodic basis. Topology broadcast or advertisement mechanisms have been developed to meet the requirement for topology updates within a network. These mechanisms are generally either timer driven or event driven. Topology broadcast, when triggered in each node by the timer or by occurrence of the particular event, is realized by the transmission of network topology information from each node to the nodes in the remainder of the network. Networks that rely on timer driven topology updates can be storing faulty topology information when the network is dynamic and rapidly changing.
While it is important to insure that the network topology information is accurate and up to date, it is also important to avoid flooding the network and consuming the available link bandwidth with these update messages. A tradeoff must be made between accuracy of the stored network topology information at the network nodes and efficient bandwidth usage in the network. Frequent topology parameter updates will insure accuracy and simultaneously devour bandwidth. Infrequent updates preserve the available bandwidth while allowing the network information stored in the nodes to become stale and outdated, thereby increasing the potential for making incorrect routing decisions.
In U.S Pat. No. 5,671,357, an additional timer is used to suppress successive event driven topology broadcasts occurring within a predetermined time interval measured from an initial event occurrence. This technique preserves available link bandwidth by suppressing repeated event driven update messages. In U.S. Pat. No. 4,825,206, a status message, such as a route failure message, is fed back to nodes along the route and causes those nodes to update their network topology databases indicating that the route is inoperative. This technique reduces the number of subsequent status messages generated by the network.
In spite of the attempts to improve the accuracy of the stored network topology information and to improve the efficiency of available bandwidth utilization when updating network topology information, the presently known techniques do not optimize the accuracy or the broadcast efficiency of stored network topology information between broadcast or advertised updates.